Catechin content of 18 teas and a green tea extract supplement correlates with the antioxidant capacity

Our literature review of currently available data in the area of tea and cancer prevention demonstrated that there is more conclusive evidence for the chemopreventive effect of green tea compared with black tea. We suggest that this is due to a large variation of the flavanol content in tea, which is not taken into consideration in most of the epidemiological studies. It was the purpose of this study to determine the flavanol content of various teas and tea products and to correlate it with their radical scavenging activity. A modified oxygen radical absorbance capacity (ORAC) assay at pH 5.5 was utilized. The total flavavol content varied from 21.2 to 103.2 mg/g for regular teas and from 4.6 to 39.0 mg/g for decaffeinated teas. The ORAC value varied from 728 to 1686 trolox equivalents/g tea for regular teas and from 507 to 845 trolox equivalents/g for decaffeinated teas. There was a significant correlation of flavanol content to ORAC value (r = 0.79, P = 0.0001) for the teas and green tea extract. The large variation in flavanol content and ORAC value among various brands and types of tea provides critical information for investigators using tea in studies of nutrition and cancer prevention.     

Comparison of the antioxidant activity of roasted tea with green, oolong, and black teas

Although the antioxidant properties of green, oolong, and black teas have been well studied, antioxidant activity has not been examined in roasted tea. Therefore, in the current studies, we investigated the antioxidant activity of roasted tea in comparison with those of green, oolong, and black teas. Using water extracts of the various teas, we examined the total phenolic content as well as the antioxidant activities, including the reducing power, the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity, and the inhibition of hemolysis caused by 2,2'-azo-bis(2-amidinopropane) dihydrochloride (AAPH)-induced lipid oxidation in erythrocyte membranes. The roasted tea contained lower levels of total phenolics than green, oolong, or black tea (green tea > oolong tea > black tea > roasted tea). The relative reducing power and DPPH scavenging activity decreased in the following order: green tea > roasted tea > oolong tea > black tea. Also, green tea was more effective against AAPH-induced erythrocyte hemolysis than other teas (green tea>roasted tea = oolong tea = black tea). These results suggest that roasted tea is beneficial to health, in humans, because of its high antioxidant activity.     

Comparison of the antioxidant activity of roasted tea with green,oolong, and black teas

Although the antioxidant properties of green, oolong, and black teas have been well studied, antioxidant activity has not been examined in roasted tea. Therefore, in the current studies, we investigated the antioxidant activity of roasted tea in comparison with those of green, oolong, and black teas. Using water extracts of the various teas, we examined the total phenolic content as well as the antioxidant activities, including the reducing power, the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity, and the inhibition of hemolysis caused by 2,2’-azo-bis(2-amidinopropane) dihydrochloride (AAPH)-induced lipid oxidation in erythrocyte membranes. The roasted tea contained lower levels of total phenolics than green, oolong, or black tea (green tea>oolong tea>black tea>roasted tea). The relative reducing power and DPPH scavenging activity decreased in the following order: green tea>roasted tea>oolong tea>black tea. Also, green tea was more effective against AAPH-induced erythrocyte hemolysis than other teas (green tea>roasted tea=oolong tea=black tea). These results suggest that roasted tea is beneficial to health, in humans, because of its high antioxidant activity.     

Tea polyphenols and theaflavins are present in prostate tissue of humans and mice after green and black tea consumption

Green and black tea have shown promise in the chemoprevention of prostate cancer. The objective of this study was to determine the bioavailability and bioactivity of tea polyphenols (PP) and theaflavins in human serum and human and mouse tissues. A decaffeinated black tea diet was administered to C57BL/6 mice. PPs and theaflavins were found in the small and large intestine, liver, and prostate in conjugated and free forms. The relative prostate bioavailability of theaflavin was 70% higher than that of epigallocatechin gallate (EGCG). In the second mouse study, a green tea (GT) diet was administered followed by the control diet for 1-5 d. Epicatechin (EC), EGCG, and epicatechin gallate (ECG) concentrations in prostate tissue were significantly decreased after 1 d of consuming the control diet. Epigallocatechin gallate (EGC), however, did not decrease significantly. For the human study, 20 men scheduled for surgical prostatectomy were randomly assigned to consume 1.42 L daily of GT, BT, or a caffeine-matched soda control (SC) for 5 d before radical prostatectomy. Tea PPs were greater in prostate samples from men consuming BT and GT than in men consuming SC (P = 0.0025). Although tea PP were not detectable in serum, ex vivo LNCaP prostate cancer cell proliferation was less when cells were grown in media containing patient serum collected after BT (P < 0.001) and GT (P = 0.025) consumption relative to baseline serum This is the first human study to show that tea polyphenols and theaflavins are bioavailable in the prostate where they may be active in the prevention of prostate cancer.     

绿茶提取物的安全性分析评价

目的　对调节血糖产品-绿茶提取物的安全性进行评价。方法　采用急性经口毒性试验、蓄积毒性试验、小鼠骨髓嗜多染红细胞微核试验、V79细胞基因突变试验对绿茶提取物的急性毒性、蓄积毒性、遗传毒性进行观察。结果　该提取物对雌、雄性小鼠急性经口LD50 均>10 0 0 0mg/ (kg·bw) ,属于实际无毒级;对动物蓄积系数K >5 ,属于弱蓄积性;对小鼠骨髓细胞未产生致畸变作用;对体外培养的中国仓鼠肺细胞(V79) ,无论直接作用和代谢活化后作用,均未呈现致突变性。结论　绿茶提取物是一种安全的调节血糖制剂。     

In vivo antioxidant effect of green tea

OBJECTIVE: The object of this study was to investigate the in vivo antioxidant effect of green tea and dosage effect of green tea on antioxidant effect. DESIGN: We tested 10 healthy subjects (aged 23-25 y, five women and five men) with overnight fasting. The total antioxidant capacity of plasma was measured at baseline and 60 min and 120 min after ingestion of 150 ml green tea. Green tea was prepared by infusing 2.5 g of dried green tea leaves for 2 min at 80 degrees C in 150 ml of water. In the second week, they took 300 ml of tea (5.0 g of green tea leaves) and, in the third week, 450 ml of tea (7.5 g of green tea leaves). The total antioxidant capacities of plasma were determined with a Total Antioxidant Kit (Randox Laboratories Ltd, UK) using a Cobas Mira analyser (Roche Diagnostic Systems Inc., Switzerland). The mean intra-assay coefficient of variation was 1.2%. RESULTS: The total antioxidant capacity of plasma increased by 1.1% at 60 min and 2.1% at 120 min over baseline value in subjects consuming 150 ml of green tea, which was statistically not significant. However, total antioxidant capacity of plasma after consuming 300 ml of green tea showed a significant increase of 7.0% after 60 min and 6.2% after 120 min (P<0.0001), and after consuming 450 ml 12.0% after 60 min and 12.7% after 120 min over baseline value (P<0.0001). CONCLUSIONS: Total antioxidant capacity of plasma was significantly increased after taking green tea in amounts of 300 and 450 ml. A positive increment according to green tea dosage was also observed. SPONSORSHIP: This work was funded by the Pacific Corporation (Korea).     

Bioavailability and catabolism of green tea flavan-3-ols in humans

ObjectiveThe aim of this study was to investigate green tea flavan-3-ol catabolism and plasma pharmacokinetic and urinary excretion by high-performance liquid chromatography with tandem mass spectrometry to evaluate their absolute bioavailability by taking into account all known and some unknown catabolites deriving from their interaction with the gastrointestinal tract and its host microflora.MethodsA feeding study was carried out in 20 healthy human volunteers who ingested 400 mL of a ready-to-drink green tea containing approximately 400 μmol of flavan-3-ols. Urine and plasma were collected for 4 and 24 h, respectively, and 39 relevant catabolites were identified in these biological fluids by tandem mass spectrometry.ResultsIn biological fluids, 39 relevant flavan-3-ol catabolites were identified. In plasma, (?)-epigallocatechin-3-gallate was the only unmetabolized compound and the highest in absolute concentration compared with (?)-epigallocatechin and (?)-epicatechin conjugates. Colonic microflora-derived polyhydroxyphenyl-γ-valerolactones were by far the main urinary catabolites, averaging 10 times greater concentratin than flavan-3-ol conjugates. The calculated bioavailability was equal to 39% and it is interesting to notice the great variability in urinary excretion of colonic metabolites among participants, probably related to differences in their own colonic microflora.ConclusionThis study demonstrates that green tea catechins are more bioavailable than previously observed when colonic ring fission metabolites are taken into consideration. Regular consumption of ready-to-drink green tea containing flavan-3-ols allows a non-marginal exposure of the human body to these catabolites, somehow justifying the numerous beneficial actions described as linked to green tea intake.     

Bioavailability of coffee chlorogenic acids and green tea flavan-3-ols

This paper reviews recent human studies on the bioavailability of chlorogenic acids in coffee and green tea flavan-3-ols in which the identification of metabolites, catabolites and parent compounds in plasma, urine and ileal fluid was based on mass spectrometric methodology. Both the chlorogenic acids and the flavan-3-ols are absorbed in the small intestine and appear in the circulatory system predominantly as glucuronide, sulfate and methylated metabolites. Even when absorption occurs in the small intestine, feeding studies with ileostomists reveal that substantial amounts of the parent compounds and some of their metabolites appear in ileal fluid indicating that in volunteers with a functioning colon these compounds will pass to the large intestine where they are subjected to the action of the colonic microflora. A diversity of colonic-derived catabolites are absorbed into the bloodstream and pass through the body prior to excretion in urine. There is growing evidence that these compounds, which were little investigated until recently, are produced in quantity in the colon and form a key part of the bioavailability equation of flavonoids and related compounds that occur in fruits, vegetables and beverages. Recent evidence indicates that some colon-derived phenolic acids have in vitro anti-inflammatory activity.     

Green tea consumption and chronic atrophic gastritis: a cross-sectional study in a green tea production village

Chronic atrophic gastritis (CAG) is well known as a precancerous lesion of the stomach, and Helicobacter pylori (H. pylori) infection increases the risk of CAG. While recent studies have reported that green tea consumption decreases the risk of gastric cancer, there has been no study analyzing the relationship between green tea consumption and the both risks H. pylori infection and CAG. We conducted a cross-sectional study on 636 subjects living in a farming village in Japan to examine the relationship among green tea consumption, H. pylori infection, and CAG. Smoking, alcohol drinking, consumption of four beverages, including green tea, and of five foods were investigated as lifestyle factors that may affect H. pylori infection and CAG. The measurement of H. pylori-IgG antibodies was used to define H. pylori infection, and serum pepsinogens were used to define of CAG. The unconditional logistic regression model was used for analyzing each odds ratio (OR). H. pylori infection was positively associated with the risk of CAG (OR = 3.73; 95% confidence interval [CI], 2.59-5.36). High green tea consumption (more than 10 cups per day) was negatively associated with the risk of CAG, even after adjustment for H. pylori infection and lifestyle factors associated with green tea consumption (OR = 0.63; 95% CI, 0.43-0.93). These results support the hypothesis that high green tea consumption prevents CAG.     

Theaflavins in black tea and catechins in green tea are equally effective antioxidants

Green tea catechins, including (-)-epicatechin (EC), (-)-epicatechin gallate (ECG), (-)-epigallocatechin (EGC) and (-)-epigallocatechin gallate (EGCG), are oxidized and dimerized during the manufacture of black tea and oolong tea to form orange-red pigments, theaflavins (TF), a mixture of theaflavin (TF1), theaflavin-3-gallate (TF2A), theaflavin-3'-gallate (TF2B) and theaflavin-3,3'-digallate (TF3). The present study was designed to compare the antioxidant activities of individual TF with that of each catechin using human LDL oxidation as a model. All catechins and TF tested inhibited Cu(+2)-mediated LDL oxidation. Analysis of the thiobarbituric acid-reactive substances (TBARS) and conjugated dienes produced during LDL oxidation revealed that the antioxidant activity was in the order: TF3 > ECG > EGCG > or = TF2B > or = TF2A > TF1 > or = EC > EGC. Four TF derivatives also demonstrated a dose-dependent antioxidant activity in Cu(+2)-mediated LDL oxidation at concentrations of 5-40 micromol/L. These results demonstrate that the TF present in black tea possess at least the same antioxidant potency as catechins present in green tea, and that the conversion of catechins to TF during fermentation in making black tea does not alter significantly their free radical-scavenging activity.     

Identification and antioxidant activity of several pigments from the residual green tea (Camellia sinensis) after hot water extraction.

Antioxidant activity of green tea extract or tea-derived polyphenols has been extensively studied. However, antioxidant activity in the non-polyphenolic fraction of green tea has been poorly analyzed. In the present study, we analyzed the antioxidant activity of the non-polyphenolic fraction of the residual green tea (Camellia sinensis) after hot water extraction using the aluminum chloride method. The non-polyphenolic fraction of residual green tea caused a significant suppression against hydroperoxide generation from oxidized linoleic acid in a dose-dependent manner. When the concentrate of the non-polyphenolic fraction was applied to a silica gel TLC plate and developed, six color spots were observed, which were considered to be chlorophylls a and b, pheophytins a and b, carotenoids, such as beta-carotene and lutein according to their specific colors, Rf values of silica gel TLC and spectrophotometric properties. Among these pigments, pheophytins a and b showed relatively abundant amounts, and the second major group of the pigment was chlorophylls a and b, and carotenoids such as beta-carotene and lutein indicated lower concentrations. Although all these pigments exhibited significant antioxidant activities, the ranks of suppressive activity against hydroperoxide generation were chlorophyll a > lutein > pheophytin a > chlorophyll b > beta-carotene > pheophytin b. These results suggest that the non-polyphenolic fraction of residual green tea has a potent suppressive activity against hydroperoxide generation from oxidized linoleic acid, which is derived from the antioxidant activities of chlorophylls a and b, pheophytins a and b, beta-carotene and lutein. This finding also implies that the combined intake of polyphenols in water-soluble fraction and antioxidative pigments in the non-polyphenolic fraction of green tea will be more efficient to prevent life style-related chronic diseases.     

The combined effects of capsaicin, green tea extract and chicken essence tablets on human autonomic nervous system activity

The purpose of this study was to investigate whether combined capsaicin, green tea, and chicken essence tablets (CCGC) enhance human autonomic nervous activities (ANS) associated with thermogenic sympathetic activity without any adverse effect on the cardiac depolarization-repolarization period. Six healthy males (25.2 +/-1.7 y) volunteered for this experiment. Autonomic nervous activities were examined 5-min at rest per 30-min for total 1.5 h after consuming chicken or CCGC or placebo tablets at random on separate days. Using heart rate variability power spectral analysis, we assessed human autonomic nervous activities. In comparison to chicken essence or placebo tablets, it was observed that the consumption of CCGC significantly increased human autonomic nervous activities [Total power representing over-all ANS activity; CCGC trial 160.2 (50.0) vs. placebo 92.8 (53.3)%, p < 0.05; VLF, very low-frequency power associated with thermogenic sympathetic activity: CCGC trial 235.5 (101.7) vs. chicken 130.5 (52.9)%, p < 0.05; LF, low frequency power representing combined sympatho-vagal activity: CCGC trial 199.8 (59.8) vs. placebo 120.6 (49.2)%, p < 0.05] at 60-min and 90-min. There were no significant differences in heart rate corrected cardiac recovery time (RTc) or QT interval (QTc). In conclusion, the consumption of CCGC enhances thermogenic sympathetic activity compared to that of chicken essence or placebo tablets. Therefore, these results suggest that combined capsaicin, green tea, and chicken essence tablets may be a beneficial food ingredient improving human autonomic nervous activities, particularly thermogenic sympathetic activity as a modulator of energy metabolism without any adverse effects on cardiac electrical stability.     

Consumption of black, green and herbal tea and iron status in French adults

OBJECTIVE: A number of potential health effects have lately been accorded to tea consumption. It is, however, not clear whether an increase in tea consumption increases the risk of iron depletion in a normal apparently healthy adult population. We have therefore evaluated this. DESIGN: Cross-sectional study. SUBJECTS: A total of 954 men (aged 52-68 years) and 1639 women (aged 42-68 years), who were participants of SU.VI.MAX Study, completed a detailed questionnaire on tea consumption. To determine the iron status of the participants, a venous blood sample was drawn and serum-ferritin was measured. Iron depletion was defined as a serum ferritin concentration <16 microg/l. Three 1-day food records were used to estimate the intake of other dietary enhancing or inhibiting factors of iron absorption, which were included in the logistic regression models. RESULTS: The mean serum-ferritin concentration was not related to black, green and herbal tea consumption in men, pre- or postmenopausal women. Also the risk of iron depletion was in the multivariate model not related to any kind of tea drinking or to the strength of tea, the infusion time or the time of tea drinking. CONCLUSIONS: The data suggest that normal apparently healthy adults are not at risk of iron depletion owing to any kind of tea drinking.     

A new antioxidant beverage produced with green tea and apple

Green tea and apple are natural products with health benefits. These healthy properties are linked closely to the antioxidant compounds, mainly phenolic compounds. These antioxidant compounds have a potential for preventing and treating cancer, cardiovascular, inflammatory and neurodegenerative diseases in humans. The aim of the present work was to design a new beverage with high antioxidant power combining extracts of green tea and apple, studying the antioxidant composition and activity, organoleptic properties (colour) and stability status during storage at different temperatures. The majority compounds identified in the beverage were flavan-3-ols, being the (?)-epigallocatechin-3-gallate which had the highest concentration. After storage, floridzine was the compound with lower decrease of concentration. The new designed beverage had a good colour, and high antioxidant activity and stability at room temperature, so that the beverage needs no refrigeration, showing potential for the development of new healthy functional beverages.     

Occurrence of vitamin B12 in green, blue, red, and black tea leaves

Vitamin B12 contents of green (0.046-0.263 and 0.125-0.535 microg/100 g dry weight), blue (0.068-0.081 and 0.525-0.528 microg/l00 g dry weight), red (0.061 and 0.663 microg/100 g dry weight), and black (0.104-0.859 and 0.305-1.20 microg/100 dry weight) tea leaves were obtained by intrinsic factor-chemiluminescence and microbiological methods, respectively. Although vitamin B12 was found in all tea leaves tested by both assay methods, the higher values by the microbiological method were not due to occurrence of both deoxyribosides and deoxynucleotides (known as an alkali-resistant factor), but may have been due to that of inactive corrinoid compounds for mammals in the tea leaves.     

Study on reduction of acrylamide in fried bread sticks by addition of antioxidant of bamboo leaves and extract of green tea

This paper investigated the efficiency of antioxidant of bamboo leaves (AOB) and extract of green tea (EGT) on the reduction of acrylamide in fried bread sticks and summarized the optimal levels of two additives. Seven experimental groups including a control group were organized for both of additives. Fried bread sticks were made via traditional processing technology. The flour was mixed with different levels (0.002-4.9 g/kg flour) of AOB and EGT, respectively. The acrylamide level in fried bread sticks was determined by liquid chromatography tandem mass spectrometry (LC-MS/MS). The sensory evaluation was performed in double blind manner. Results showed that nearly 82.9% and 72.5% of acrylamide were reduced when the AOB and EGT addition levels were 1 and 0.1 g/kg, respectively. The elevated inhibitory effects of AOB and EGT on the acrylamide formation were achieved with an increase of additive levels unless the spiking levels of AOB and EGT were greater than 1 and 0.1 g/kg, respectively. Sensory evaluation results showed that the flavor and texture of fried bread sticks processed by AOB and EGT had no significant difference compared to normal food matrixes (p>0.05) when both AOB and EGT addition levels were no more than 1 g/kg. The present study indicated that both AOB and EGT could significantly reduce the acrylamide content generated in fried bread sticks and keep original flavor and crispness of fried bread sticks. This study could be regarded as an important contribution on the reduction of acrylamide by natural antioxidants.     

Acute effects of ingestion of black and green tea on lipoprotein oxidation

BACKGROUND: Tea has been associated with a reduced risk of cardiovascular disease. One proposed mechanism of this risk reduction involves inhibition of lipoprotein oxidation in vivo by antioxidant polyphenolic compounds derived from tea. However, controlled interventions uniformly failed to show that ingestion of tea can inhibit LDL oxidation ex vivo. The absence of effects in previous studies may be due to the isolation of LDL particles from polyphenolic compounds that are present in the aqueous phase of serum. OBJECTIVE: The objective of this study was to examine the acute effects of ingestion of black and green tea on ex vivo Cu(2+)-induced lipoprotein oxidation without prior isolation of lipoproteins from serum. DESIGN: The acute effects of 4 hot drinks-green tea and black tea (each at a dose equivalent to 4 standard cups), water matched to the teas for caffeine content, and water-were assessed in 20 healthy men by using a Latin-square design. The lag time to lipoprotein diene formation, slope of the propagation phase of the oxidation curve, and area under the oxidation curve were calculated. Urinary concentrations of 4-O-methylgallic acid were used as a marker of uptake and metabolism of polyphenolic compounds from tea. RESULTS: Significant increases in urinary 4-O-methylgallic acid for black and green tea (P < 0. 0001) were observed. Caffeine did not significantly influence lipoprotein oxidation. Compared with the water control, there was a greater lag time for black tea (5.4 +/- 2.9 min; P = 0.05) that was of borderline significance and a similar trend for green tea (4.4 +/- 2.8 min; P = 0.17). Slope and area under the oxidation curve were not altered. CONCLUSION: Black tea has a mild acute effect on ex vivo lipoprotein oxidation in human serum. 2000;71:-7.